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Description of key information

Repeated ingestion by both rats and dogs results in an adaptive enlargement of liver as indicated by the increase in relative liver weight with mild changes in clinical parameters. Higher dosages affect body weight, spleen and kidneys. Both for chronic feeding to rats and subchronic feeding to dogs a NOEL of 1000 ppm was determined. For dogs, this corresponds to a daily average intake of 31.7 mg/kg bw for males and of 43.6 mg/kg bw for females. For rats it is in the range of  47 —  58 mg/kg bw/day.  In a subacute study with gavage dosing, the NOEL was 30 mg/kg bw for females and less than 30 mg/kg bw for males (MHLW 2007). 

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
47 mg/kg bw/day
Study duration:

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

In the oldest study (Feron 1966) a total of 80 Wistar rats, 10 males and 10 females per dose group, were feed with 0, 0.2, 1.0 and 5.0 % for three months. It is described in detail, but not all endpoints required in the respective OECD testing guideline were assessed. Ophthalmological examinations were not performed and clinical biochemistry parameters were not evaluated.

The findings are compared to common strain characteristics, but no historical control data included in the report. No individual data for each animal and no absolute organ weights are given. Growth rate, food consumption and food efficiency of the rats fed 1 and 5 % in the rations were decreased only in the first two weeks of the study and these effects disappeared thereafter. There were no relevant changes in laboratory parameters (haematology, clinical chemistry) except from the males of the 5 % level which showed a decreased number of erythrocytes and an increased number of leukocytes. There was a dose dependent tendency of organ weight increase of the liver, kidney and spleen. The histopathological investigation revealed kidney lesions, however, nephrotic changes were noted only in the males of the 1.0 and 5 % feeding level group.

In liver, slight centrilobular hypertrophy of parenchymal cells was observed in a few animals: At 5%, each 5 males and females; 1% - 7 males and 1 female; 0.2% - 2 males; control: none. No differences in glycogen and fat content were observed. Liver findings are described as "Central zones of the lobules much less stainable than the peripheral zones. In the central zones somewhat enlarged parenchymal cells with slightly swollen nuclei". Two males of the highest dose group showed distinct pathological liver changes consisting of bile duct proliferation, an increased number of Kupffer cells, extended sinusoids and often enlarged parenchymal cells with irregular nuclei. This observation was not consistently seen. No abnormalities were seen in the following organs at microscopic examination: brain, pituitary, spinal cord, femoral nerve, bone marrow, gastrointestinal tract, testis, epididymis, ovary, adrenal, and salivary gland.

The NOEL was the 0.2 % concentration in the diet, corresponding to a daily intake of approximately 150 mg/kg bw.




In the subchronic feeding study with beagles (Gfeller 1981a), the substance was administered to 48 dogs (6 males and 6 females per dose group) in the diet for 3 months at dosages of 0, 1'000, 3'000 and 10'000 ppm. The study design appears to follow OECD Guideline 409 (1998) and the report contains sufficient detail to suggest GLP-like characteristics, but no statement of certification. However dated and signed Quality Assurance Inspection statements are included. For each dose group, a recovery group with each one male and one female were included.

No deaths occurred during the study. The food consumption of group 4 (10,000 ppm) was reduced for both male and female dogs. At the 3'000 and 10'000 ppm levels, the animals showed changes in blood chemistry parameters: Elevated levels of the alanin-aminotransferase (GPT) and gamma-glutamyl-transpepdidase (GGT). For females and males, the relative liver weight was increased by 21% (p < 0.05 compared to control) and 28% at 10000 ppm (p < 0.01 for dose-dependent trend) at the end of the treatment period. This was not observed in animals of the recovery groups. No experimental significance is attributed to the decreased mean thyroid to body weight ratio at the highest dose group in male dogs (p < 0.05).

No other gross or microscopical changes in the organs and tissues related to the treatment were noted. No impairment of the auditory perception was found. The NOEL was 1'000 ppm corresponding to a daily average intake of 31.7 mg/kg bw for males and of 43.6 mg/kg bw for females.


The key study is the 104 weeks chronic toxicity study with rats (Hunter 1975) because its design is consistent with the OECD testing guideline for chronic toxicity 452 and the reporting detail is sufficient for assessment. The study was performed prior to introduction of GLP. A total of 500 CFY rats (50 male and 50 female per dose group) were treated with the test article in the diet, at dose levels of 0, 100, 300, 1000 and 3000 ppm in the diet per day. Chemical analysis of the test item in the feed confirmed the nominal concentrations.

No clinical symptoms and no substance-related mortality were observed. At 3000 ppm a small reduction of body weight gain among males during the second year of treatment and slightly reduced food intake among females during the period 53 to 80 weeks of treatment were observed. Organ weight analysis performed on rats killed after 104 weeks of treatment revealed slightly heavier thyroid/parathyroid weights among treated animals, which only attained a level of statistical significance among males treated with 1000 ppm and females treated with 1000 or 3000 ppm when related to bodyweight, and among females treated with 100, 1000 or 3000 ppm when related to brain weight.

After statistical re-evaluation of significance levels in comparison with control using Williams' test, for the males, no significant treatment effects were detected. For females significant increases in both absolute kidney (p < 0.05) and thyroid weights (p < 0.01) were found in both 1000 and 3000 ppm treatment groups. Although statistically significant, there is no dose-response relationship. As the values obtained for treated rats were within the normal range for CFY rats, the differences were considered to have arisen fortuitously.

Based on the above findings it was concluded that 1000 ppm (47-58 mg/kg bodyweight/day) was the no-effect level. The findings at 3000 ppm are difficult to assess.


There are two further reports on subchronic (Carlson 1969) and subacute (Gysling 1958) exposure of rats via feed which are inadequate in quality. The results of both studies are consistent with the findings of the valid studies.

A subacute study with gavage application was performed in 2006 on behalf of MHLW. A summary report in Japanese language was prepared in 2008. This is information is compiled from the english translation. The GLP compliant study followed OECD testing guideline 422 with satellite groups for a 14 -day recovery period. Olive oil was used as vehicle. The outcome of this study confirms the effects on liver and kidney. A NOEL of 30 mg/kg bw was reported for females, with adverse findings on liver and kidney at doses of 100 mg/kg bw and 300 mg/kg bw. For males, relative liver effects were increased at the lowest dose group of 30 mg/kg bw. The puplic information does not include a table with relative organ weights. Considering that neither absolute liver weights nor body weights were affected at this dose level and that histopathology findings for liver were only observed at 300 mg/kg bw, 30 mg/kg bw are considered to be the overall NOAEL.

No changes were observed in clinical observations, reflex/reaction, grip strength, locomotor activity, body weight and food consumption. Urinalysis showed increased protein in the males given 100 mg/kg and above, but this change was recovered by the discontinuance of dosage.

No effect on hematological parameters was observed in any dosed group of either sex. The plasma levels of phospholipid in the group of both sexes given 300 mg/kg, and of total cholesterol in the females given 300 mg/kg were increased. These changes had disappeared by the end of the recovery period.

Relative liver weight was increased in the males given 30 mg/kg and above. Absolute liver weight was increased in the males given 300 mg/kg alone. In the females, both absolute and relative organ weights were increased in the liver of the 100 mg/kg and 300 mg/kg-dosed groups, and in the kidneys of the 300 mg/kg-dosed group. These changes had disappeared by the end of the recovery period.

In the histological examination, liver and kidney lesions occurred in the dosed group of both sexes. The hepatic lesions were characterized by increased incidences of hypertrophy of the centrilobular hepatocytes in the males given 300 mg/kg and in the females given 100 mg/kg and above. Theses changes were not observed at the end of the recovery period. The kidney lesions exhibited a gender difference, as characterized by increased incidences of an eosinophilic body of proximal tubules in the males given 300 mg/kg, and hydropic change and regeneration of proximal tubules in the females given 100 mg/kg and above. The eosinophilic body of proximal tubules remained affected in the recovery group of males given 300 mg/kg, whereas female kidney lesions were not observed in the satellite females given 300 mg/kg.

The lower effect levels in this study are attributed to bolus dosing, as the substance is efficiently taken up after ingestion. The NOEL derived from the chronic feeding studies (47 mg/kg bw) is considered to be relevant for DNEL derivation as it represents a more realistic human exposure situation.

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
Most relevant dosing scheme (feed more appropriate compared to gavage).

Repeated dose toxicity: via oral route - systemic effects (target organ) digestive: liver; urogenital: kidneys

Justification for classification or non-classification

 Classification, Labeling, and Packaging Regulation (EC) No. 1272/2008

The available experimental test data are reliable and suitable for classification purposes under Regulation 1272/2008. As a result the substance is not considered to be classified for oral repeated dose toxicity under Regulation (EC) No. 1272/2008